Impact absorbing system for a flat switch panel

ABSTRACT

An impact absorbing system for a flat switch panel has an impact spacer. The impact spacer, a rigid layer that is fixed to an energy-absorbing layer, attaches to the top surface of a flat switch panel just under the overlay. During a condition of switch abuse, the impact absorbing system disperses the energy from a high impact actuation force over a large area of the rigid layer, which in turn causes a large volume of energy-absorbing layer material to be deformed, directing the otherwise damaging impact away from a raised part of the switch that normally accepts a user provided actuation force. Preferably there is an embossed area in the rigid layer and a pip on the raised part of the switch, both improving the function and tactile feedback of the switch. The most preferred embodiment includes a polycarbonate backer on the bottom of the flat switch panel to additionally protect switch components from being damaged by a high impact actuation force.

BACKGROUND OF THE INVENTION

[0001] Numerous devices are operated when a user presses a pushbutton located on a flat switch panel. Increasingly, such devices are set up at locations that are not monitored, such as ATM machines and gas pumps. If a single switch on a device fails, the entire device must be shut down until the failed switch can be repaired or replaced. As designed, pushbutton switches on a flat panel are intended to be operated by a fingertip and, preferably, give a tactile feedback to the user. Unfortunately, careless and impatient users cause most flat switch panel failures. Gas pump pushbutton switches, for example, are frequently operated by the tip of a gas nozzle that is struck against the flat switch panel for the purpose of actuating a particular switch. It is desirable to have a sealed switch for devices that are exposed to the elements and to harmful contaminants. A magnetically-coupled pushbutton switch is one type of flat panel switch that may be sealed and offers good tactile feedback to a user, but a magnetically-coupled pushbutton switch includes a sheet metal armature that is relatively thin compared to a gas nozzle.

[0002] Magnetically-coupled switches have a metal armature that is normally held spaced from switch contacts by a sheet magnet. A user-provided actuating force applied to the armature causes it to snap free of the sheet magnet and close the switch contacts by electrically connecting them. Release of the actuating force allows the magnet to attract the armature back to a normal position, in coupled engagement with the magnet so the armature is spaced from the switch contacts, to reopen the switch. A magnetically-coupled switch typically has the switch contacts formed on a non-conductive substrate. A non-conductive spacer layer is fixed to the substrate, with an opening in the spacer layer exposing the switch contacts. The sheet magnet overlies the spacer layer. The armature is magnetically-coupled to the bottom of the sheet magnet so that the armature is housed within the opening in the spacer layer. Preferably, the armature has a crown that protrudes through an aperture in the magnet layer. Most often, a polyester membrane layer with suitable graphics overlies the magnet layer to direct a user of the switch as to location and function of the switch. The benefits of magnetically-coupled pushbutton switches have been demonstrated in U.S. Pat. Nos. 5,523,730, 5,666,096, 5,990,772 and 6,069,552, incorporated herein by reference.

SUMMARY OF THE INVENTION

[0003] The present invention concerns an impact spacer that protects a pushbutton armature from being damaged during high impact actuation. The impact spacer is installed under a switch overlay, the overlay usually being a thin polyester sheet that has graphics printed thereon to show a user where various switches are located on a flat switch panel. The impact spacer is preferably a thick sheet of polycarbonate plastic adhesively fixed to a thick sheet of silicone rubber. When a high impact force is directed at a flat switch panel, the crown of an armature is susceptible to being crushed. The impact spacer protects the armature and crown by spreading the energy of a high impact force throughout a large volume of the impact spacer materials. The polycarbonate plastic layer is rigid, so it spreads a localized impact laterally across a large area of the flat switch panel. The underlying sheet of silicone rubber dissipates the energy that has been spread out over a large area of the impact spacer by deforming and compressing to absorb the excess force delivered to the flat switch panel. Under a normal actuation force, there is very little deformation of the silicone rubber layer so that the tactile feedback delivered by the armature is crisply transferred to a user.

[0004] Preferably, the polycarbonate plastic layer of the impact spacer has an embossed area above each pushbutton switch. The embossed area prevents excessive preloading of switches so that thicker impact spacers may be used. Additional features of the switch of the present invention include a pip on the crown of an armature to preserve good tactile feedback, and a backer that is fixed to the bottom of the flat switch panel to protect a circuit layer of the switch against bending and cracking. Electrical leads connect the circuit layer of the switch to electronics that are external to the switch. Electrical conductors on the circuit layer are arranged within the switch so that the pushbutton armature of the switch is movable into and out of shorting relationship with the electrical conductors to change the circuit logic for a circuit incorporating the switch. As used herein, the term “top” refers to that surface of any part in a cross sectional figure of the drawings that faces the top edge of the page, while “bottom” refers to that surface of any part in a cross sectional figure of the drawings that faces the bottom edge of the page.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005]FIG. 1 is a cross-section of an impact absorbing system according to the present invention incorporated for use with a magnetically-coupled pushbutton switch.

[0006]FIG. 2 is a cross-section similar to FIG. 1, but with a second type of impact spacer.

[0007]FIG. 3 is an exploded perspective view of the switch and impact absorbing system of FIG. 1.

[0008]FIG. 4 is an exploded perspective view of the impact spacer of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

[0009] As shown in FIGS. 1 through 4, the impact absorbing system of the present invention always includes an impact spacer 2 that has a rigid layer 4 and an energy-absorbing layer 6, but there are several additional features shown and described in the foregoing description that, though preferred, are not necessary and may be excluded from the impact absorbing system where cost or preference dictates otherwise. FIGS. 1 and 3 show the ideal impact absorbing system as it would appear on a magnetically-coupled pushbutton switch 8, or other flat panel switch that would benefit from the impact absorbing system of the present invention. An impact absorbing system that is capable of providing good tactile feedback and a very high level of protection for a flat switch panel will preferably include the following features: an embossed area 10 on the rigid layer 4; a selective adhesive layer, not shown, between the impact spacer 2 and the magnetically-coupled pushbutton switch 8; a reinforcement backer 12; and a pip 14 on the switch armature 16. Preferred materials and methods of attachment will be discussed, but these preferences are not intended to exclude other suitable or functionally equivalent materials or methods of attachment.

[0010]FIG. 1 shows a magnetically-coupled pushbutton switch 8, similar to the ones shown and described in the aforementioned U.S. Patents, that has been modified to incorporate the impact absorbing system of the present invention. A magnetically-coupled pushbutton switch 8 typically includes, from the top down, a magnet coupler layer 22, an aperture 24 through the magnet coupler layer, a metal armature 16 having a crown 26 that protrudes through the aperture, a spacer layer 28 that defines a switch cavity 30, and a substrate 32 that has electrical conductors formed thereon. The impact spacer 2 of the present invention is fixed to the top of the magnet coupler layer 22 such that the energy-absorbing layer 6 is on or adjacent the crown 26 of the armature 16. A thin polyester overlay 18 covers the impact spacer 2.

[0011] As already mentioned, the impact absorbing system of the present invention always includes an impact spacer. The impact spacer 2 is preferably made from two different sheets of material that are adhesively bonded to each other by an elastomeric adhesive. General adhesive, such as acrylic adhesive, will suffice, but the elastomeric adhesive is preferred because of its superior ability to permanently bond the layers of the impact spacer together. The top sheet of the impact spacer 2 is the rigid layer 4, while the bottom sheet of the impact spacer is the energy-absorbing layer 6. During an impact, the rigid layer 4 spreads a localized impact over a larger area of the energy-absorbing layer 6. The energy-absorbing layer 6 compresses and changes shape to disperse the energy of the impact throughout a large volume of the energy-absorbing layer material. Some of the force from the localized impact is transferred through the energy-absorbing layer 6 to depress the pushbutton armature 16 and actuate the switch, but the armature is protected from being crushed or bent because of the impact spacer 2.

[0012] The rigid layer 4 of the impact spacer 2 is preferably a sheet of polycarbonate material, such as Lexan®, having a thickness of between ten and thirty thousandths of an inch. Other materials that could be used as the rigid layer include polyester, nylon, vinyl, carbon fiber materials, or other similar materials that offer some flexibility, but are substantially impervious to compression and fracturing. The thickness of the rigid layer is often dependent upon the material selected for use as the rigid layer. There must be enough flexibility in the rigid layer so that finger pressure will cause the rigid layer to adequately flex during switch actuation. The finger pressure, or user provided actuation force, is typically in the range of five to fifteen ounces, but for some applications is fifty ounces or higher. If the desired material to be used as the rigid layer 4 is well suited for use as the overlay 18, appropriate graphics may be printed on the rigid layer 4 so that the rigid layer takes the place of the overlay that normally covers and protects a flat switch panel. If there is concern that the graphics will wear off, the rigid layer may be transparent with the graphics printed on the bottom surface of the rigid layer. FIGS. 1 through 4 show a separate overlay 18 that would typically be adhesively fix to the top of the rigid layer 4.

[0013] Where the rigid layer covers pushbuttons on a flat switch panel that are in close proximity to each other, it may be necessary to isolate actuation forces so that a user provided actuation force applied to one pushbutton switch does not spread out over the rigid layer and cause a nearby pushbutton switch to also be actuated. Additionally, the stiffness of some rigid layer materials may cause the armature 16 to be excessively preloaded so that the switch does not fully return to an un-actuated position, or the stiffness may negatively affect the tactile feedback of a pushbutton switch making it difficult for a user to recognize whether an actuation force was adequate. An isolation structure that prevents accidental actuation of a pushbutton adjacent the pushbutton intended to receive a user provided actuation force is recommended. The preferred isolation structure is an embossed area on the rigid layer that is around each area that will be above a switch. FIGS. 1 and 3 show an embossed area 10 in the rigid layer 4. Note that the embossing causes the area of the rigid layer 4 above each switch to bulge away from the switch. For most purposes, the size of each embossed area 10 is approximately the size of an average fingertip, or roughly one third of a square inch. The embossed area 10 improves flexibility of the rigid layer 4 just above the pushbutton, but the increase flexibility does not significantly affect the ability of the rigid layer to disperse the energy of a high impact force over a large area of the rigid layer.

[0014]FIGS. 2 and 4 show a second type of isolation structure that utilizes a supplemental rigid layer 5 that is adhesively fixed to the bottom of the rigid layer 4. Preferably, the rigid layer 4 in FIGS. 2 and 4 is polyester and the supplemental rigid layer 5 is polycarbonate, but the layers may be any of the materials previously listed for use as the rigid layer. The supplemental rigid layer 5 has cutouts 11 that align with an area above each pushbutton, that area being about the size of a fingertip. As can be seen in FIG. 4, the cutouts 11 in the supplemental rigid layer 5 may include passages that allow for pressure changes within the cutouts to be vented, thereby keeping the tactile feedback more uniform. The supplemental rigid layer 5 additionally spaces the rigid layer 4 from each switch armature 16 so that preloading is better controlled. The rigid layer 4 of FIGS. 2 and 4 is typically thinner than the embossed rigid layer of FIGS. 1 and 3 because the thickness of the supplemental rigid layer 5 contributes to the ability of the impact spacer to spread the energy of a high impact actuation over a large area of the energy-absorbing layer 6. The supplemental rigid layer 5 does not cover a pushbutton, making it easier for a user to actuate the switch because less force is required to flex just the rigid layer 4. The main benefit of using an isolation structure is to allow the impact spacer to be thicker than would otherwise be possible. Without an isolation structure, the thickness of the rigid layer 4 is significantly limited because of problems with excessive preloading and loss of tactile feedback.

[0015] In FIGS. 1 through 4, the energy-absorbing layer 6 of the impact spacer 2 is preferably a sheet of silicone rubber material having a thickness of between thirty and eighty thousandths of an inch. There are, of course, numerous other materials that mimic the energy-absorbing property of silicone rubber such as, but not limited to, other rubber materials, gelatins and foams. The energy-absorbing layer 6 dissipates a lot of the energy of a high impact actuation force by deforming and compressing a large volume of the energy-absorbing layer material. The energy-absorbing layer 6 is usually in direct contact with the crown 26 of each pushbutton switch that is part of the flat switch panel. This direct contact causes mild preloading of each switch. Preloading normally does not result in a bulge on the top surface of the rigid layer 4 because the energy-absorbing layer 6 slightly compresses and deforms around the crown 26. Under a normal actuation force, the energy-absorbing layer 6 is compressed above the crown 26 of a pushbutton until a breakaway force is achieved. The breakaway force causes the pushbutton to move into contact with electrical conductors of the switch. The compressed portion of the energy-absorbing layer material travels with the crown 26 during switch travel. There is a tactile feedback to the user when the pushbutton abruptly meets the substrate 32 of the switch. That tactile feedback is crisply transferred through the compressed portion of the energy-absorbing layer 6 to the rigid layer 4 and overlay 18.

[0016] An additional feature of the impact spacer 2 that is recommended is to use a selective adhesive layer, not shown, to fix the pushbutton switch 8 to the bottom of the energy-absorbing layer 6. Adhesive layers are usually about five thousandths of an inch thick. By selective, it is meant that there are areas on the energy-absorbing layer 6 that do not receive adhesive. These areas that do not receive adhesive are above each pushbutton switch. If adhesive were left above each pushbutton switch, the energy-absorbing layer 6 could bind during actuation and prevent the switch from returning normally to an un-actuated position. Another benefit of the selective adhesive layer is that the energy-absorbing layer 6 has more freedom of movement so that it can deform more than would be possible if it were adhered to the pushbutton. Where the energy-absorbing layer 6 is silicone rubber, a silicone adhesive, such as elastomeric adhesive made by 3-M corporation, should be used so that the impact spacer 2 is permanently fixed to the switch panel.

[0017] Depending on the material of the substrate 32, there may be a need for additional support under the substrate 32. If the substrate 32 is likely to flex so much during high impact actuation that the armature 16 may bend, or the substrate is likely to fracture, then a backer 12 should be attached to the bottom of the substrate. The backer 12 is a layer of material that provides additional support to the substrate 32 and is also capable of absorbing excess energy from a high impact actuation force. The backer 12 is preferably polycarbonate, but could also be sheet metal, wood, cork, or any of the rigid layer materials previously mentioned.

[0018] For ultra high impact actuation forces, the thickness of the impact spacer should be increased. However, making a thicker impact spacer usually is at the cost of tactile feedback to the user. If it is necessary to use an impact spacer 2 that is very thick, the armature crown 26 should include a pip 14. The pip 14 is a small raised area on the top of the crown 26. The pip 14 is an extension of the crown 26 that allows the crown to extend farther into the energy-absorbing layer 6 so that tactile feedback can be focused and transferred through the pip 14 to the user. The pip 14 brings the top of the armature crown 26 closer to the user so that the required actuation force is lower than it would be without the pip. Because the pip 14 has very little surface area, it can poke into the energy absorbing material without contributing very much to preloading. Although the relatively small area of the pip reduces the magnitude of force directed toward the armature crown, focusing the actuation force onto the pip enhances the tactile feedback to a user.

[0019] While a preferred form of the invention has been shown and described, it will be realized that alterations and modifications may be made thereto without departing from the scope of the following claims. For example, the impact spacer 2 could be made from a single material, such as a thermoplastic elastomer, that can function as both the rigid layer 4 and the energy-absorbing layer 6, but the materials cost of such an alternative was not competitive at the time of invention. 

What is claimed is:
 1. A method of making an impact absorbing system, for use with a flat switch panel that has at least one pushbutton switch, comprising the steps of: fabricating an impact spacer having a rigid layer with a top and bottom and an energy-absorbing layer with a top and bottom; forming at least one isolation structure in the rigid layer; attaching the bottom of the rigid layer to the top of the energy-absorbing layer; installing the impact spacer onto the flat switch panel so that the energy-absorbing layer is intermediate the rigid layer and the at least one pushbutton switch of the flat switch panel.
 2. The method of claim 1 wherein the step of forming an isolation structure in the rigid layer is characterized by embossing an area of the rigid layer that is above the at least one pushbutton switch of the flat switch panel.
 3. The method of claim 1 wherein the step of forming an isolation structure in the rigid layer is characterized by a forming a supplemental rigid layer, the supplemental rigid layer having at least one cutout that is above the at least one pushbutton switch of the flat switch panel, the top of the rigid layer substantially covering the supplemental rigid layer and the at least one cutout.
 4. The method of claim 1 further comprising the step of positioning a backer on the flat switch panel such that the at least one pushbutton switch is intermediate the backer and the impact spacer.
 5. The method of claim 1 further comprising the step of forming a pip on the at least one pushbutton switch of the flat switch panel such that the pip will protrude into the energy-absorbing layer of an installed impact spacer.
 6. The method of claim 1 wherein the step of installing the impact spacer is characterized by the use of a selective adhesive layer, the selective adhesive layer not adhering to areas on the flat switch panel that are substantially above a pushbutton switch.
 7. An impact spacer, for use with a flat switch panel that has at least one pushbutton switch, comprising: a rigid layer with a top and bottom; an isolation structure in the rigid layer; an energy-absorbing layer with a top and bottom; a means of attaching the bottom of the rigid layer to the top of the energy-absorbing layer; and a means of attaching the bottom of the energy-absorbing layer to the flat switch panel.
 8. The impact spacer of claim 7 wherein the isolation structure is an embossed area in the rigid layer that lies above the at least one pushbutton switch on the flat switch panel.
 9. The impact spacer of claim 7 wherein the isolation structure is formed by making the rigid layer from at least a first and second sheet of rigid layer material, the first sheet of the rigid layer includes the bottom of the rigid layer and has at least one cutout where the rigid layer covers the at least one pushbutton of the flat switch panel, the second sheet of the rigid layer includes the top of the rigid layer and substantially covers the first sheet and the at least one cutout.
 10. The impact spacer of claim 7 wherein the means of attaching the energy-absorbing layer to the flat switch panel is by a selective adhesive layer, the selective adhesive layer not adhering to areas on the flat switch panel that are substantially above a pushbutton switch.
 11. An impact absorbing system, for use with a pushbutton switch having a magnetically-coupled armature, comprising: an impact spacer having a rigid layer with a top and bottom and an energy-absorbing layer with a top and bottom; a means of attaching the bottom of the rigid layer to the top of the energy-absorbing layer; a means of attaching the bottom of the energy-absorbing layer to a top surface of the pushbutton switch;
 12. The impact absorbing system of claim 11 wherein the rigid layer includes an isolation structure.
 13. The isolation structure of claim 12 wherein the isolation structure is an embossed area of the rigid layer that is at least partially above the pushbutton switch.
 14. The isolation structure of claim 12 wherein the isolation structure includes at least a first and second sheet of rigid layer material; the second sheet is a supplemental rigid layer, the supplemental rigid layer having a cutout that is above the pushbutton switch; the first sheet substantially covers the supplemental rigid layer and the cutout.
 15. The impact absorbing system of claim 11 wherein the magnetically-coupled armature has a crown that protrudes through an aperture in a sheet magnet coupler layer of the pushbutton switch, the crown further comprising a pip that protrudes into the energy-absorbing layer of the impact absorbing system.
 16. The impact absorbing system of claim 15 wherein the rigid layer includes an isolation structure.
 17. The impact absorbing system of claim 16 further comprising a backer and a means of attaching the backer to the pushbutton switch so that the pushbutton switch is intermediate the impact spacer and the backer.
 18. The impact absorbing system of claim 11 further comprising a backer and a means of attaching the backer to the pushbutton switch so that the pushbutton switch is intermediate the impact spacer and the backer.
 19. The impact absorbing system of claim 11 wherein the means of attaching the bottom of the energy-absorbing layer to a top surface of the pushbutton switch is by a selective adhesive layer, the selective adhesive layer not providing a means of attaching the energy-absorbing layer to an area of the pushbutton switch that is at least partially above the armature.
 20. The impact absorbing system of claim 17 wherein the means of attaching the bottom of the energy-absorbing layer to a top surface of the pushbutton switch is by a selective adhesive layer, the selective adhesive layer at least not extending over an area that is above the crown of the magnetically-coupled armature. 